Comment 21 for bug 1927277

Reviewed: https://review.opendev.org/c/openstack/charm-nova-compute/+/873282
Committed: https://opendev.org/openstack/charm-nova-compute/commit/acb628e214e1ae2f88c97d036a86a33e4faea46b
Submitter: "Zuul (22348)"
Branch: stable/xena

commit acb628e214e1ae2f88c97d036a86a33e4faea46b
Author: Aurelien Lourot <email address hidden>
Date: Mon Sep 27 15:52:48 2021 +0200

    Process subordinate releases packages map

    For principal - subordinate plugin type relations where the
    principal Python payload imports code from packages managed by a
    subordinate, upgrades can be problematic.

    This change will allow a subordinate charm that have opted into the
    feature to inform its principal about all implemented release -
    packages combinations ahead of time. With this information in place
    the principal can do the upgrade in one operation without risk of
    charm relation RPC type processing at a critical moment.

    This makes use of
    https://github.com/juju/charm-helpers/pull/643

    This is similar to
    https://review.opendev.org/c/openstack/charm-keystone/+/781822

    Also fixed broken link to charm-guide.

    Note, that this includes a ch sync as part of the cherry-pick to pick up
    the charm-helpers functions.

    Change-Id: Iaf5b44be70ee108cbe88b4a26f0f15f915d507fe
    Closes-Bug: #1927277
    (cherry picked from commit 8fb37dc0c1f76754f9b94863317af03b770516cd)